When receiving oil from oil wells containing a mixture of hydrocarbons and water, it is desirable to separate the hydrocarbons from the water and reinject the water either above or below the producing zone. Apparatus and methods have been proposed that make it possible to separate hydrocarbons from water and to reinject the water.
U.S. Pat. No. 5,456,837 to Peachey teaches a method of downhole cyclone oil/water separation that utilizes a cyclone separator. The cyclone separator includes a separation chamber, wherein liquids of differing densities are separated. The separator has at least one mixed liquids inlet through which liquids pass into the separation chamber, a first outlet for liquids of a first density range to pass out of the separation chamber and a second outlet for liquids of a second density range to pass out of the separation chamber. Although Peachey teaches the use of multiple separators inside of a separation chamber, Peachy does not teach a method wherein liquids are separated multiple times to facilitate more complete separation.
A difficulty with using a single separator is that some formations need disposal water to contain very low concentrations of oil. Otherwise, the ability of some injection formations to accept the disposal fluid is reduced.